1. Field of the Invention
The invention relates to human adapted antibodies which bind human tissue factor, an antigen present on extra vascular tissues including tumor cells, which antibodies do not inhibit tissue factor mediated blood coagulation. The invention also relates to methods of using the antibody to treat conditions such as cancer that are associated with the presence and receptor functions of human tissue factor.
2. Discussion of the Field
Tissue Factor (TF), also known as coagulation factor III (F3), tissue thromboplastin, or CD142 is a transmembrane glycoprotein having a 219 amino acid extracellular domain comprising two fibronectin type III domains and a short intracellular domain with one serine residue capable of being phosphorylated. TF is the cellular receptor for FVII/FVIIa.
TF exhibits a tissue-specific distribution with high levels in the normal brain, lung and placenta and low levels in the spleen, thymus, skeletal muscle and liver in the form of a cellular receptor. It is also found in cell-derived microparticles and as an alternatively spliced soluble form. In addition to the expression in normal tissue, TF has been reported to be over-expressed in most major tumor types and in many tumor-derived cell lines (Ruf W J Thromb Haemost. 5:1584-1587, 2007; Milsom et al., Arterioscler Thromb Vasc Biol. 29: 2005-2014, 2009).
Coagulation of serum proteins in response to injury is an important physiological response to injury. Exposure of the blood to proteins including collagen (intrinsic pathway) and tissue factor (extrinsic pathway) initiates changes to blood platelets and the plasma protein fibrinogen, a clotting factor. Following damage to a blood vessel, factor VII (FVII) leaves the circulation and comes into contact with tissue factor (TF) expressed on tissue-factor-bearing cells (stromal fibroblasts and leukocytes), forming an activated TF-FVIIa complex. TF-FVIIa activates factor IX (FIX) and factor X (FX). FVII can be allosterically activated by TF and activated by thrombin, FXIa, plasmin, FXII and FXa. TF-FVIIa forms a ternary complex with FXa.
Tissue factor (TF) expression by nonvascular cells plays an essential role in hemostasis by activating blood coagulation. TF is further associated with processes distinct from hemostasis and directly related to functions at the surface of cells on which it is expressed. TF-dependent assembly of coagulation proteases on vascular and nonvascular cells activates protease activated receptors (PARs) which are G-protein-coupled receptors. Thus, the TF:VIIa complex is capable of inducing cell signaling, through PARs, primarily PAR2 (Camerer et al., Proc. Natl. Acad. Sci. USA 97:5255-5260, 2000; Riewald & Ruf, Proc. Natl. Acad. Sci. USA 98:7742-7747, 2001; Ruf et al, J Thromb Haemost 1: 1495-4503, 2003; Chen et al., Thromb Haemost 86: 334-45, 2001) contributing to tumorigenesis, angiogenesis, tumor progression, and metastasis.
The ternary complex TF/FVIIa/FXa is formed directly by the TF:VIIa complex acting on FX or indirectly after TF:VIIa cleavage of FIX to FIXa which can cleave FX to FXa. The TF/FVIIa/FXa complex formation may result in signaling or activate other receptors such as PAR1-4. TF/FVIIa/FXa complex formation leads to the induction of Interleukin-8 (IL-8), which can stimulate tumor cell migration (Hjortor et al., Blood 103:3029-3037, 2004). Both PAR1 and PAR2 are involved in tumor metastasis (Shi et al., Mol Cancer Res. 2:395-402, 2004), however, the activated binary and ternary complexes, TF-VIIa and TF-VIIa-FXa, are activators of PAR2 which also leads to cell signaling (Rao & Pendurthi, Arterioscler. Thromb. Vasc. Biol. 25:47-56, 2005). Therefore, it was of interest to determine whether the oncogenic role of tissue factor could be separated from the procoagulant role, which had also long been suspected to be involved in tumor migration, extravasation, and metastatic mechanisms.
Monoclonal antibodies such as those described by Morrisey (1988, Thromb Res 52(3): 247-261; U.S. Pat. No. 5,223,427) and Magdolen (1996 Biol Chem 379: 157-165) to tissue factor have been used to explore functional and immunological aspects of the ligand binding sites. Monoclonal antibodies capable of binding tissue factor can be used to block thrombotic events by interfering with the ability of TF to form or maintain the TF-VIIa complex or by blocking the ability of the complex to activate FX. Antibodies that bind to tissue factor and do not block coagulation are also known. Factor VIIa initiated TF signaling blocking but not coagulation blocking antibodies such as the antibody 10H10 have also been described (Ahamed et al. 2006 Proc Natl Acad Sci USA 103 (38): 13932-13937) and such antibodies have provided the opportunity to study the role and utility of an agent with such activity in the treatment of solid tumors (Versteeg, et al 2008 Blood 111(1): 190-199). Ruf et al, in published application WO2007056352A3 discloses methods and compositions for inhibiting tissue factor signaling without interfering with hemostatis in a patient.
As cancer progression is a multifaceted process, a therapeutic candidate which is a TF binding antibody capable of blockade of oncogenic, metastatic, angiogenic, and anti-apoptotic functions on tumor cells while not interfering with hemostasis in a patient would be desirable.